The Entry Exit System (EES) app, designed to allow non-EU citizens to register fingerprints and a photo for EU border control remotely, will not be ready in time for its October implementation.
As a result, Eurostar passengers may experience long queues for border checks at stations instead.
The app is intended to replace passport stamping and provide greater oversight of who enters and leaves the EU.
The European Travel Information and Authorization System (ETIAS) requires UK travelers to complete initial registration before departing.
This process may cause long queues at Port of Dover, Eurostar, and Eurotunnel terminals due to French border checks.
Eurostar is preparing for the change by installing over 49 kiosks at St Pancras station and increasing staff to facilitate customer flow.
The Eurostar boss, Ms Cazenave, believes the use of the ETIAS app will make the process smoother, and while the EU has not yet launched the app, it is expected to do so soon.
The Port of Dover is anticipating queue issues due to its limited space and high volume of cars, coaches, and lorries.
A P&O Ferries director has suggested that the IT system implementation, which was initially scheduled for October, may need to be delayed again.
In response, Eurotunnel owner Getlink is constructing new processing areas at Folkestone and Calais to manage the changes.
Eurostar, the cross-Channel train operator, experienced a significant decrease in passengers and revenue during the pandemic but had recovered to pre-
Covid levels by the end of last year.